A projection display system includes a light source and an optical modulator as basic components. The light source supplies light which is manipulated by the modulator to form an image. Light sources of several colors may be used to create color images and the brighter the light source the brighter the image that can be formed.
Laser arrays are promising light sources for display applications. Arrays of high power, extended vertical cavity, surface emitting, diode lasers can be frequency doubled to provide light across the visible spectrum. As an example, Novalux, Inc. (Sunnyvale, Calif.) has demonstrated Novalux Extended Cavity Surface Emitting Lasers (NECSEL) that produce light at red, green and blue wavelengths.
Optical modulators based on linear arrays of micro-electromechanical systems (MEMS) are well suited for display applications. Such modulators manipulate the amplitude and/or phase of incident light to distribute it into patterns that form an image. Uniform illumination of a modulator is usually required to produce an image of uniform brightness.
Laser light beams often have a Gaussian intensity profile in the direction perpendicular to propagation. One way to illuminate a linear modulator array approximately uniformly with a Gaussian beam is to expand the beam so that only the central part strikes the array. Light in the lower intensity “wings” of the Gaussian profile is lost, however. What is needed is a way to efficiently use the light emitted by lasers, especially laser arrays, to uniformly illuminate linear light modulator arrays.